From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753350AbdJFJbZ (ORCPT ); Fri, 6 Oct 2017 05:31:25 -0400 Received: from foss.arm.com ([217.140.101.70]:56338 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753274AbdJFJbW (ORCPT ); Fri, 6 Oct 2017 05:31:22 -0400 Subject: Re: [PATCH v2 10/16] iommu: introduce device fault report API To: Jacob Pan , "iommu@lists.linux-foundation.org" , LKML , Joerg Roedel , David Woodhouse , Greg Kroah-Hartman , Rafael Wysocki Cc: "Liu, Yi L" , Lan Tianyu , "Tian, Kevin" , Raj Ashok , Alex Williamson References: <1507244624-39189-1-git-send-email-jacob.jun.pan@linux.intel.com> <1507244624-39189-11-git-send-email-jacob.jun.pan@linux.intel.com> From: Jean-Philippe Brucker Message-ID: <5103e49c-d74c-c697-b5f7-e5c54edce595@arm.com> Date: Fri, 6 Oct 2017 10:36:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <1507244624-39189-11-git-send-email-jacob.jun.pan@linux.intel.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jacob, On 06/10/17 00:03, Jacob Pan wrote: > Traditionally, device specific faults are detected and handled within > their own device drivers. When IOMMU is enabled, faults such as DMA > related transactions are detected by IOMMU. There is no generic > reporting mechanism to report faults back to the in-kernel device > driver or the guest OS in case of assigned devices. > > Faults detected by IOMMU is based on the transaction's source ID which > can be reported at per device basis, regardless of the device type is a > PCI device or not. > > The fault types include recoverable (e.g. page request) and > unrecoverable faults(e.g. access error). In most cases, faults can be > handled by IOMMU drivers internally. The primary use cases are as > follows: > 1. page request fault originated from an SVM capable device that is > assigned to guest via vIOMMU. In this case, the first level page tables > are owned by the guest. Page request must be propagated to the guest to > let guest OS fault in the pages then send page response. In this > mechanism, the direct receiver of IOMMU fault notification is VFIO, > which can relay notification events to QEMU or other user space > software. > > 2. faults need more subtle handling by device drivers. Other than > simply invoke reset function, there are needs to let device driver > handle the fault with a smaller impact. > > This patchset is intended to create a generic fault report API such > that it can scale as follows: > - all IOMMU types > - PCI and non-PCI devices > - recoverable and unrecoverable faults > - VFIO and other other in kernel users > - DMA & IRQ remapping (TBD) > The original idea was brought up by David Woodhouse and discussions > summarized at https://lwn.net/Articles/608914/. > > Signed-off-by: Jacob Pan > Signed-off-by: Ashok Raj > --- [...] > +int iommu_register_device_fault_handler(struct device *dev, > + iommu_dev_fault_handler_t handler) > +{ > + if (dev->iommu_fault_param) > + return -EBUSY; > + get_device(dev); > + dev->iommu_fault_param = > + kzalloc(sizeof(struct iommu_fault_param), GFP_KERNEL); > + if (!dev->iommu_fault_param) > + return -ENOMEM; > + dev->iommu_fault_param->dev_fault_handler = handler; Since the handler is owned by a device driver, you also need to clean it up when switching the driver (native->VFIO and VFIO->native), in iommu_attach_device I suppose. Thanks, Jean